(a) Field of the Invention
This invention relates to access platform systems for industrial machinery, in particular a platform arrangement which provides safe and convenient access for both machine operators and maintenance personnel to such machines. The invention is particularly concerned with access platform systems providing safe access to elevated positions on mobile earth-moving machines of all types, such as graders, bull-dozers and the like.
(b) Discussion of the Background Art
Many existing earth-moving machines merely include a step or ladder, perhaps associated with a hand rail or grip, facilitating access for operators to the control station of the machine, which station may be elevated some several metres from ground level. During operation of such machines, it is also sometimes necessary for operators to check the position or status of certain components of their machine, such as drive wheels, earth-working implements or other machine sub-systems, relative to geographical features, flora, fauna or man-made obstacles. This is especially the case when the extremities of such components are not clearly visible from the control station. A further example which may expose operators to the risk of a fall is when they simply wish to clean mud or grime from the external surfaces of cabins surrounding the control station.
Accordingly, there is a risk of injury to the operator should they slip and/or fall when climbing to an control station or standing in a precarious position elevated on the superstructure of the machine, whether to gain a better view of machine components or merely to clean cabin windows. This risk is multiplied where the machine includes earth-working implements with sharp edges or teeth, such as excavator buckets, grader blades or earth ripping tines, in the path of a potential fall. Machine operators have previously suffered serious injuries, including debilitating and potentially fatal head injuries, during falls of this nature.
Maintenance personnel and operators face similar risks when access to the engine or other operating systems, such as hydraulic lines or bearings, is required for inspection, cleaning or lubrication purposes. This is especially so when the machine is on-site rather than in a workshop where suitable access frames may be available.
An example of a prior arrangement of fixed access steps and platform with hand rails is shown in U.S. Pat. No. 4,067,588 in the name of Morge et al. and assigned to Caterpillar Tractor Co. Whilst an operator may be able to safely negotiate the rear of the cabin, this arrangement does not allow convenient access to the front of the cabin or to the power plant for maintenance purposes.
Several prior art arrangements merely comprise a simple retractable step or step and hand grip for facilitating access to an operator station as set out in the following documents. German (DD) Patent Application No. 244162 in the name of VEB Baumasch Halle describes entry steps on a grader which provide access to the driving position. The entry steps hinge at the rear end of the vehicle and are actuated by a mechanism which is interlocked with the vehicle hand controls for vehicle movement.
Japanese Patent Application No. 07-257281 in the name of Yutani Heavy Industries Ltd describes a motorised step disposed in a bracket located at the lower part of the entrance to the operator's cab on a hydraulic excavator. An electric motor rotates the step into position at an upper side on the entrance when the operator applies the brake.
U.S. Pat. No. 3,986,724 in the name of Rivinius describes a hydraulic power operated step which elevates the operator from a lower position, whereby the operator may mount the step near ground level, to an upper position adjacent the operator's cabin. This is a relatively complex and costly device in comparison to its single purpose operation, which still exposes an operator to the risk of a fall.
U.S. Pat. No. 3,997,183 in the name of Russey and assigned to Caterpillar Tractor Co describes an access step for a scraper. The step and grab handle are pivoted and interconnected for simultaneous movement, whereby movement of the grab handle extends the step to an operable position. Although much simpler in design than the Rivinius step, this device is relatively limited in function and would appear to require athleticism for the operators of larger machines.
Another aspect of desirable access arrangements for earthmoving machinery is that it should not normally obscure an operator's field of view and/or be in such a position that it might be damaged by soil, rocks or other debris which might be encountered during machine operations. The importance of not obscuring the operator's view has been recognised in U.S. Pat. No. 3,879,059 also in the name of Caterpillar Tractor Co describes a front wheel mudguard for a wheeled front-end loader which has a reinforced lattice type box section to maintain the operator's field of vision. The mudguard is detachably mounted on the excavator by releasable fastening means to facilitate replacement.
United Kingdom (GB) Patent Document No. 2291013 in the name of New Holland NV describes and access means for an agricultural vehicle such as a harvester. The access means includes a ladder and a platform operatively associated with one another so as to move from an operative position to a inoperative position. Similarly, United Kingdom (GB) Patent Document No. 2291381 in the name of Giat Industries describes a gangway and ladder assembly mounted on a motorised breakdown vehicle. The gangway and ladder are hinged to a platform on the chassis of the vehicle for movement between a raised position and a lowered position, for gaining access to the platform. The disclosed open platform arrangements pose a finite risk of injury should an operator fall from the ladder or platform when climbing to or from an elevated position.